Image display device, image display system, image display method and program

ABSTRACT

A plurality of images of an imaging subject is captured by using a plurality of cameras. The plurality of images is synthesized to generate a synthesized image viewing the imaging subject from a virtual perspective. The synthesized image is displayed on a screen ( 83 ). When a user operation for changing the position of the virtual perspective is detected, the position of the virtual perspective in the synthesized image is changed.

TECHNICAL FIELD

The present invention relates to a technology of displaying an imageindicative of surroundings of a vehicle.

BACKGROUND

A technology of synthesizing images obtained by capturing surroundingsof a vehicle such as an automobile and displaying a synthesized imageviewing the surroundings of the vehicle from a virtual perspective hasbeen known. By the technology, a user (representatively, a driver) cancheck the surroundings of the vehicle with sitting in the vehicle.

A technology of transmitting the image to a portable terminal carried bythe user has been also suggested (for example, refer to PatentLiterature 1). The user can recognize a state or theft possibility ofthe vehicle by visibly recognizing the image, even though the user is ata place remote from the vehicle.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2012-121384

SUMMARY OF INVENTION Technical Problem

According to the suggested technology, however, since the perspectivefor viewing the surroundings of the vehicle is limited, the user cannotalways visibly recognize the surrounding image from a desired angle. Forthis reason, for example, even when the user checks, on the portableterminal, an image showing that a suspicious person is approaching inthe vicinity of the vehicle, it is not clearly determined who thesuspicious person is and what the suspicious person is doing, so thatthe user's concern may be instead increased.

It is therefore an object of the present invention to change a virtualperspective to a user's desired perspective when displaying an imageindicative of surroundings of a vehicle from the virtual perspective.

Solution to Problem

In order to achieve the above object, a first aspect to be taken by thepresent invention is an image display device including:

an acquisition unit configured to acquire a plurality of images obtainedby capturing an imaging subject by using a plurality of cameras,

a generation unit configured to synthesize the plurality of images andto generate a synthesized image viewing the imaging subject from avirtual perspective,

a display control unit configured to display the synthesized image on ascreen, and

a detection unit configured to detect a user operation of changing aposition of the virtual perspective of the synthesized image displayedon the screen,

wherein the generation unit is configured to change the position of thevirtual perspective of the synthesized image on the basis of the useroperation.

According to the above configuration, since the position of the virtualperspective of the synthesized image is changed on the basis of the useroperation, it is possible to easily display the imaging subject from auser's desired perspective.

In the image display device, the synthesized image may be configured byan image viewing a reference point set at a specific position of theimaging subject from the position of the virtual perspective,irrespective of the position of the virtual perspective.

According to the above configuration, it is possible to provide thesynthesized image enabling a user to feel as if the user were movingwhile seeing the imaging subject.

In the image display device, the plurality of cameras may be mounted ona vehicle. In this case, the generation unit may be configured to changethe position of the virtual perspective on the basis of a worldcoordinate system in which the reference point is set as an origin withrespect to the vehicle and a perspective coordinate system in which thereference point is set as an origin with respect to the virtualperspective.

According to the above configuration, it is possible to display theimaging subject from diverse directions and positions.

The image display device may be configured so that a position of thereference point can be set by a user.

According to the above configuration, it is possible to display theimaging subject at a user's desired angle.

In the image display device, the generation unit may change the positionof the virtual perspective about a vertical axis of the world coordinatesystem when the user operation is an operation indicative of ahorizontal direction on the screen.

According to the above configuration, it is possible to change theposition of the virtual perspective about the vertical axis of the worldcoordinate system by a simple operation.

In the image display device, the generation unit may change the positionof the virtual perspective about a horizontal axis of the perspectivecoordinate system when the user operation is an operation indicative ofa vertical direction on the screen.

According to the above configuration, it is possible to change theposition of the virtual perspective about the horizontal axis of theperspective coordinate system by a simple operation.

In the image display device, the generation unit may change the positionof the virtual perspective within a range above a ground contact surfaceof the imaging subject when the position of the virtual perspective ischanged about the horizontal axis of the perspective coordinate system.

According to the above configuration, it is possible to set anappropriate perspective position.

In the image display device, the plurality of cameras may be mounted ona vehicle. In this case, when a user operation indicative of ahorizontal direction on the screen is performed with the reference pointbeing viewed from the virtual perspective located immediately above thevehicle, the generation unit may change the position of the virtualperspective about a longitudinal axis of the vehicle.

According to the above configuration, since the position of the virtualperspective is changed from a position immediately above the vehicle toa lateral side, it is possible to display the imaging subject whilechanging a viewing angle without uncomfortable feeling.

In order to achieve the above object, a second aspect to be taken by thepresent invention is an image display system including:

an image acquisition device, and

an image display device capable of performing communication with theimage acquisition device,

wherein the image acquisition device includes:

an acquisition unit configured to acquire a plurality of images obtainedby capturing an imaging subject by using a plurality of cameras,

a request reception unit configured to receive from the image displaydevice a request signal for requesting transmission of the plurality ofimages, and

an image transmission unit configured to transmit the plurality ofimages on the basis of the request signal,

wherein the image display device includes:

a request transmission unit configured to transmit to the imageacquisition device the request signal for requesting transmission of theplurality of images,

an image reception unit configured to receive the plurality of imagesfrom the image acquisition device,

a generation unit configured to synthesize the plurality of images andto generate a synthesized image viewing the imaging subject from avirtual perspective,

a display control unit configured to display the synthesized image on ascreen, and

a detection unit configured to detect a user operation of changing aposition of the virtual perspective of the synthesized image displayedon the screen, and

wherein the generation unit is configured to change the virtualperspective of the synthesized image on the basis of the user operation.

According to the above configuration, since the position of the virtualperspective of the synthesized image is changed on the basis of the useroperation, it is possible to easily display the imaging subject from auser's desired perspective.

In the image display system, the image acquisition device may be mountedon a vehicle. In this case, the imaging subject may be surroundings ofthe vehicle. Also, the image display system may have a security deviceconfigured to detect a previous phenomenon leading to theft of thevehicle. The security device may have a monitoring unit configured todetect the previous phenomenon and a notification unit configured tonotify the image display device of detection of the previous phenomenon.

According to the above configuration, even though a user of the imagedisplay device is at a place remote from the vehicle, the user canrecognize occurrence of the previous phenomenon leading to the theft ofthe vehicle and can rapidly check the surroundings of the vehiclethrough the screen.

In order to achieve the above object, a third aspect to be taken by thepresent invention is an image display method including:

(a) a step of acquiring a plurality of images obtained by capturing animaging subject by using a plurality of cameras;

(b) a step of synthesizing the plurality of images and generating asynthesized image viewing the imaging subject from a virtualperspective;

(c) a step of displaying the synthesized image on a screen; and

(d) a step of detecting a user operation of changing a position of thevirtual perspective of the synthesized image displayed on the screen,

wherein in step (b), the position of the virtual perspective of thesynthesized image is changed on the basis of the user operation.

According to the above configuration, since the position of the virtualperspective of the synthesized image is changed on the basis of the useroperation, it is possible to easily display the imaging subject from auser's desired perspective.

In order to achieve the above object, a fourth aspect to be taken by thepresent invention is a program configured to be executable by a computerincluded in an image display device configured to display an image. Theprogram is configured to enable the computer to execute:

(a) a step of acquiring a plurality of images obtained by capturing animaging subject by using a plurality of cameras,

(b) a step of synthesizing the plurality of images and generating asynthesized image viewing the imaging subject from a virtualperspective,

(c) a step of displaying the synthesized image on a screen, and

(d) a step of detecting a user operation of changing a position of thevirtual perspective of the synthesized image displayed on the screen,

wherein in step (b), the position of the virtual perspective of thesynthesized image is changed on the basis of the user operation.

According to the above configuration, since the position of the virtualperspective of the synthesized image is changed on the basis of the useroperation, it is possible to easily display the imaging subject from auser's desired perspective.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts an outline of an image display system according to afirst illustrative embodiment.

FIG. 2 depicts a portable terminal provided for the image display systemof FIG. 1.

FIG. 3 is a block diagram depicting a configuration of the image displaysystem of FIG. 1.

FIG. 4 depicts arrangement of cameras provided for the image displaysystem of FIG. 1.

FIG. 5 is a block diagram depicting a configuration of the portableterminal of FIG. 2.

FIG. 6 depicts a method of generating surrounding images and asynthesized image in the image display system of FIG. 1.

FIG. 7 depicts positions of virtual perspectives in the image displaysystem of FIG. 1.

FIG. 8 depicts positions of the virtual perspectives in the imagedisplay system of FIG. 1.

FIG. 9 depicts movement of the virtual perspective in the image displaysystem of FIG. 1.

FIG. 10 depicts movement of the virtual perspective in the image displaysystem of FIG. 1.

FIG. 11 depicts movement of the virtual perspective in the image displaysystem of FIG. 1.

FIG. 12 depicts movement of the virtual perspective in the image displaysystem of FIG. 1.

FIG. 13 depicts an example of a display image in the image displaysystem of FIG. 1.

FIG. 14 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 15 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 16 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 17 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 18 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 19 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 20 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 21 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 22 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 23 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 24 depicts an example of the display image in the image displaysystem of FIG. 1.

FIG. 25 is a flow chart depicting a processing sequence that is to beexecuted by the image display system of FIG. 1.

FIG. 26 is a flow chart depicting a processing sequence that is to beexecuted by the image display system of FIG. 1.

FIG. 27 is a block diagram depicting a configuration of the portableterminal of the image display system according to a second illustrativeembodiment.

FIG. 28 depicts movement of the virtual perspective in the image displaysystem of FIG. 27.

FIG. 29 depicts movement of the virtual perspective in the image displaysystem of FIG. 27.

FIG. 30 depicts an example of the display image in the image displaysystem of FIG. 27.

FIG. 31 is a flow chart depicting a processing sequence that is to beexecuted by the image display system of FIG. 27.

FIG. 32 is a flow chart depicting a processing sequence that is to beexecuted by the image display system of FIG. 27.

FIG. 33 depicts a modified embodiment of the image display system.

DESCRIPTION OF EMBODIMENTS

Hereinafter, illustrative embodiments of the present invention will bedescribed with reference to the drawings.

1. First Illustrative Embodiment

<1-1. Outline>

FIG. 1 depicts an outline of an image display system 1 according to anillustrative embodiment. The image display system 1 has an imageacquisition device 3 and cameras 4 (4F, 4B, 4L, 4R) mounted on a vehicle2. The image display system 1 is a system for displaying surroundingimages of the vehicle 2, which are to be acquired from the cameras 4(4F, 4B, 4L, 4R) by the image acquisition device 3, on a portableterminal 8. The portable terminal 8 is carried by a user remote from thevehicle 2.

In the system, the vehicle 2 is mounted with a security device 5 havinga monitoring sensor. The monitoring sensor operates when a suspiciousperson is excessively approaching the vehicle 2 or does physical harm tothe vehicle 2, and the security device 5 notifies the user that themonitoring sensor has operated. The user having received a notificationfrom the security device 5 requests the image acquisition device 3 totransmit an image, and the surrounding image of the vehicle 2 isdisplayed on the portable terminal 8. At this time, the user freelychanges a range within which the image is displayed, and refers to asurrounding situation of the vehicle 2 at a desired angle.

FIG. 2 depicts an example of the portable terminal 8 having a display 83configured to display the surrounding image of the vehicle 2. The usercan change a display range of the image and check a concerned part indetail by operating a touch panel 83 a of the display 83. The userrefers to the surrounding image of the vehicle 2, and can remotelyoperate an alarm of the vehicle 2 or notify a security company, asrequired. By using the image display system 1, even when the user is ata place remote from the vehicle 2, the user can safely keep the vehicle2 all the time.

<1-2. Configuration>

Subsequently, the respective devices mounted on the vehicle 2 andconfiguring the image display system 1 are described with reference toFIG. 3. The vehicle 2 has the image acquisition device 3, the cameras 4,the security device 5, and an alarm unit 6.

The image acquisition device 3 is an electronic control deviceconfigured to receive image data from the cameras 4 mounted on thevehicle and to transmit the received image data to the portable terminal8. The image acquisition device 3 has a control unit 31, a communicationunit 32 and a storage unit 33.

The control unit 31 is a microcomputer having a CPU, a RAM and a ROM.The control unit 31 is connected in communication with the otherconfigurations of the image acquisition device 3, and is configured tocontrol overall operations of the device. The control unit 31 has arequest reception unit 31 a, a camera control unit 31 b, an imageacquisition unit 31 c, an image transmission unit 31 d and an antitheftunit 31 e.

The request reception unit 31 a is configured to receive a requestsignal for requesting operations and capturing start of the cameras 4from the user having the portable terminal 8.

When the request reception unit 31 a receives the request signal forcapturing start from the user, the camera control unit 31 b transmits anoperation signal to the cameras 4 to cause the cameras 4 to start thecapturing.

The image acquisition unit 31 c is configured to acquire image datatransmitted from the cameras 4 and to convert the acquired image datainto a format that can be processed in the control unit 31.

The image transmission unit 31 d is configured to transmit the imagedata, which is acquired from the cameras 4 by the image acquisition unit31 c, to the portable terminal 8 through the communication unit 32.

The antitheft unit 31 e is configured to transmit an operation signal tothe alarm unit 6 to cause the alarm unit 6 to issue an alarm. Thereby,the vehicle 2 is prevented from being thieved. In the meantime, theantitheft unit 31 e may also be configured to cause the alarm unit 6 toissue an alarm and to control an engine control device (not shown) sothat an engine is not operated. Also, the antitheft unit 31 e may beconfigured to notify a security company through the communication unit32. That is, the antitheft unit 31 e may be configured to prevent thevehicle 2 from being thieved by using a device provided for the vehicle2.

The communication unit 32 has a communication function using wirelesscommunication, and is configured to perform information communicationwith the portable terminal 8 through a network 7. As the informationcommunication technology to be used, WiMAX (Worldwide Interoperabilityfor Microwave Access), LTE (Long Term Evolution) or the like may beexemplified.

The storage unit 33 is a memory configured to store therein data. Forexample, a non-volatile storage medium such as an EEPROM (ElectricalErasable Programmable Read-Only memory), a flash memory, a hard diskdrive having a magnetic disk and the like may be cited. Also, thestorage unit 33 has a program 33 a.

The program 33 a is firmware that is read out by the control unit 31 andis executed so as to control the image acquisition device 3 by thecontrol unit 31.

In the below, the cameras 4 are described. The cameras 4 include a frontcamera 4F, a rear camera 4B, a left side camera 4L and a right sidecamera 4R. The cameras 4F, 4B, 4L, 4R have a lens and an imagingelement, respectively, and are disposed at different positions of thevehicle 2.

FIG. 4 depicts positions at which the cameras 4 (4F, 4B, 4L, 4R) aredisposed at the vehicle 2 and directions in which optical axes of therespective cameras face. The front camera 4F is provided at a front endportion of the vehicle 2, and an optical axis 4Fa thereof is made toface towards a straight-ahead direction of the vehicle 2. The rearcamera 4B is provided at a rear end portion of the vehicle 2, and anoptical axis 4Ba thereof is made to face towards an opposite directionto the straight-ahead direction of the vehicle 2, i.e., a backwarddirection. The left side camera 4L is provided at a left side-viewmirror ML, and an optical axis 4La thereof is made to face towards aleft direction of the vehicle 2 (a direction orthogonal to thestraight-ahead direction). The right side camera 4R is provided at aright side-view mirror MR, and an optical axis 4Ra thereof is made toface towards a right direction of the vehicle 2 (a direction orthogonalto the straight-ahead direction).

The respective cameras 4F, 4B, 4L, 4R are configured to capture thesurroundings of the vehicle 2 in different directions and toelectronically acquire captured images. The lens of the camera 4 has afocal distance shorter than a standard lens and a 180 degree or greaterangle of view θ. For this reason, it is possible to capture the entiresurroundings of the vehicle 2 by using the four cameras 4.

As shown in FIG. 3, the security device 5 is a device configured todetect a previous phenomenon leading to theft of the vehicle 2 or anarticle in the vehicle 2, and to notify the portable terminal 8 carriedby the user of the vehicle 2 that theft concern has occurred, through anelectronic mail. The security device 5 has a monitoring sensor 5 a and amail notification unit 5 b.

The monitoring sensor 5 a is a sensor configured to detect a previousphenomenon leading to theft of the vehicle 2 or an article in thevehicle 2. For example, a vibration sensor configured to detectvibrations generated in the vehicle 2, a glass breaking sensorconfigured to detect breaking of a glass of the vehicle 2, aninclination sensor configured to detect inclination of the vehicle 2caused by a jack or a crane, an invasion sensor configured to detect aninvader into the vehicle 2, and the like may be cited.

When the monitoring sensor 5 a detects the previous phenomenon leadingto the theft, the mail notification unit 5 b notifies the user that thetheft concern has occurred. Specifically, the mail notification unit 5 bis configured to generate an electronic mail having contents that thetheft concern has occurred and to transmit the electronic mail to theportable terminal 8 carried by the user. Rather than text informationusing the electronic mail, the notification may be made by voiceinformation. In this case, the portable terminal 8 may be configured toread the voice information by speech. When the security device 5 has aplurality of monitoring sensors, the mail notification unit 5 b ispreferably configured to include information, which indicates that whichmonitoring sensor has detected the previous phenomenon leading to thetheft, into the electronic mail. This is to enable the user to easilyrecognize the situation of the vehicle 2.

The alarm unit 6 is a device configured to make a voice to thesurroundings for warning. The alarm unit 6 may be a speaker or hornmounted to the vehicle 2, for example. The alarm unit 6 may be a unitconfigured to emit light, such as a warning indicator mounted to thevehicle 2, in addition to the unit configured to make a voice. Forexample, the alarm unit 6 may be configured to call attention to thesurroundings for warning.

The portable terminal 8 is an information terminal carried by the userand having a function for displaying an image, a connection function toan information network, and the like. For example, the portable terminal8 may be a portable phone or a smart phone. FIG. 5 depicts aconfiguration of the portable terminal 8. The portable terminal 8 has acontrol unit 81, a communication unit 82, the display 83 and a storageunit 84.

The control unit 81 is a microcomputer having a CPU, a RAM and a ROM.The control unit 81 is connected in communication with the otherconfigurations of the portable terminal 8, and is configured to controloverall operations of the portable terminal 8. The respective functionsof the control unit 81 will be described later.

The communication unit 82 has a communication function using wirelesscommunication, and is configured to perform information communicationwith the image acquisition device 3 and the security device 5 throughthe network 7. As the wireless communication technology to be used,WiMAX (Worldwide Interoperability for Microwave Access), LTE (Long TermEvolution) or the like may be exemplified.

The display 83 is configured to display a variety of information such asletters, figures and the like and to visually present the information tothe user. The display 83 is a display device such as a liquid crystalmonitor, a plasma display, an organic EL display or the like, forexample. The display 83 has the touch panel 83 a.

The touch panel 83 a is configured to detect a user's touch on a buttonarea displayed on the display 83 and to transmit the detected positioninformation to the control unit 81.

The storage unit 84 is a memory configured to store therein data. Forexample, a non-volatile storage medium such as an EEPROM (ElectricalErasable Programmable Read-Only memory), a flash memory, a hard diskdrive having a magnetic disk and the like may be cited. Also, thestorage unit 84 has vehicle body image data 84 a and a program 84 bstored therein.

The vehicle body image data 84 a is image data representing an outwardappearance of the vehicle 2. The vehicle body image data 84 a includesimage data that is prepared while assuming a case where the vehicle 2 isviewed from all angles of the outside. The vehicle body image data 84 amay be acquired from an external server through the network 7 afterattaching the image acquisition device 3 to the vehicle 2, instead ofstoring the same in advance in the portable terminal 8. In this case,the vehicle body image data 84 a coinciding with the outward appearanceof the vehicle 2 having the image acquisition device 3 attached theretocan be acquired. The user may request the vehicle body image data 84 aby transmitting a vehicle name or the like of the vehicle 2 to theexternal server from the portable terminal 8.

The program 84 b is firmware that is read out by the control unit 81 andis executed so as to control the portable terminal 8 by the control unit81.

The respective functions of the control unit 81 are described. Thecontrol unit 81 has an image acquisition unit 81 a, an image generationunit 81 b, a display control unit 81 c and an operation detection unit81 d.

The image acquisition unit 81 a is configured to acquire the image datatransmitted from the image acquisition device 3 and to convert theacquired image data into a format that can be processed in the controlunit 81. That is, the image acquisition unit 81 a is configured toacquire the plurality of images obtained by capturing the imagingsubject by using the plurality of cameras 4.

The image generation unit 81 b is configured to synthesize the pluralityof captured images acquired from the cameras 4 and to generate asurrounding image indicative of the surroundings of the vehicle 2 viewedfrom a virtual perspective. The virtual perspective is a perspectivelooking down the vehicle 2 from a position outside the vehicle 2. Theimage generation unit 81 b is configured to superimpose a vehicle bodyimage indicative of the vehicle 2 viewed from the virtual perspective onthe surrounding image. A method of generating the surrounding image bythe image generation unit 81 b and a method of setting the virtualperspective will be described later.

The display control unit 81 c is configured to display data such as animage, letters and the like on the display 83. The display control unit81 c is also configured to change an image and the like to be displayedon the display 83, based on a touch position input to the touch panel 83a.

The operation detection unit 81 d is configured to detect a useroperation on the touch panel 83 a. Specifically, the operation detectionunit 81 d is configured to detect which direction a user's fingertipmoves on the touch panel 83 a after it touches the touch panel 83 a,based on the touch position information transmitted from the touch panel83 a.

As the user operation on the touch panel 83 a, a flick operation ofcontacting and sliding the fingertip on the touch panel 83 a, a pinch-inoperation of shortening an interval between the fingertip and thefingertip with the two fingertips being contacted to the touch panel 83a, and a pinch-out operation of widening an interval between thefingertip and the fingertip with the two fingertips being contacted tothe touch panel 83 a may be exemplified.

The notification unit 81 e is configured to transmit a predeterminedsignal to a device outside the portable terminal 8 through thecommunication unit 82. As the signal to be transmitted by thenotification unit 81 e, a signal for requesting the image acquisitiondevice to transmit the image data may be exemplified.

<1-3. Generations of Surrounding Image and Synthesized Image>

In the below, a method by which the image generation unit 81 b generatesa surrounding image AP indicative of a surrounding area of the vehicle 2and a synthesized image CP having the vehicle body image 10 superimposedon the surrounding image AP is described. FIG. 6 depicts a method bywhich the image generation unit 81 b generates the surrounding image AP.

First, when the front camera 4F, the rear camera 4B, the left sidecamera 4L and the right side camera 4R capture the surroundings of thevehicle 2, respectively, four images AP(F), AP(B), AP(L), AP(R)indicative of the front, the rear, the left side and the right side ofthe vehicle 2 are acquired. The four images include the image datarepresenting the entire surroundings of the vehicle 2.

The image generation unit 81 b projects the data (values of respectivepixels) included in the four images AP(F), AP(B), AP(L), AP(R) to aprojection plane TS, which is a three-dimensional curved surface in avirtual three dimensional space. The projection plane TS has asubstantially semispherical shape (a bowl shape), for example. A centralpart (a bottom part of the bowl) of the projection plane TS is definedas a position of the vehicle 2. Also, parts except for the central partof the projection plane TS are associated with any one of the imagesAP(F), AP(B), AP(L), AP(R), respectively.

The image generation unit 81 b projects the surrounding images AP(F),AP(B), AP(L), AP(R) to the parts except for the central part of theprojection plane TS. The image generation unit 81 b projects the imageAP(F) of the front camera 4F to a part of the projection plane TS, whichcorresponds to the front of the vehicle 2, and projects the image AP(B)of the rear camera 4B to a part of the projection plane TS, whichcorresponds to the rear of the vehicle 2. Also, the image generationunit 81 b projects the image AP(L) of the left side camera 4L to a partof the projection plane TS, which corresponds to the left side of thevehicle 2, and projects the image AP(R) of the right side camera 4R to apart of the projection plane TS, which corresponds to the right side ofthe vehicle 2. Thereby, the surrounding image AP indicative of theentire surrounding areas of the vehicle 2 is generated.

Then, the image generation unit 81 b sets a virtual perspective VPfacing from any perspective position in the three-dimensional spacetowards any line of sight. Then, the image generation unit 81 b cutsimage data projected to an area of the projection plane TS, which isincluded in a view angle as seen from the set virtual perspective VP. Bythe cut image data, the surrounding image AP indicative of thesurrounding areas of the vehicle 2 viewed from the virtual perspectiveVP is generated.

The image generation unit 81 b reads out the vehicle body image datafrom the storage unit 84, and generates the vehicle body image 10 of thevehicle 2 viewed from the virtual perspective VP. Then, the imagegeneration unit 81 b synthesizes the vehicle body image 10 into thesurrounding image AP indicative of the surrounding areas of the vehicle2 viewed from the virtual perspective VP, thereby generating asynthesized image CP.

When a virtual perspective VPt of which a perspective position is setimmediately above the vehicle 2 and the line of sight is made to faceimmediately downward is set, the image generation unit 81 b generates asynthesized image CPt looking down the vehicle 2 and the surroundingareas of the vehicle 2 by using the surrounding images AP(F), AP(B),AP(L), AP(R) and the vehicle body image 10. The synthesized image CPt isan image looking down the vehicle 2 from immediately above the vehicleand represents the surrounding areas of the vehicle 2.

Also, when a virtual perspective VPb of which a perspective position isset at a front-upper position of the vehicle 2 and the line of sight ismade to face towards a rear-lower direction of the vehicle 2, the imagegeneration unit 81 b generates a synthesized image CPb looking down thevehicle 2 and the surrounding areas of the vehicle 2 by using thesurrounding images AP(B), AP(L), AP(R) and the vehicle body image 10.The synthesized image CPb is an image looking down the rear of thevehicle 2 from a front-upper side and represents the rear area of thevehicle 2.

Also, when a virtual perspective VP1 of which a perspective position isset at an oblique left-rear and upper position of the vehicle 2 and theline of sight is made to face towards a front-lower direction of thevehicle 2, the image generation unit 81 b generates a synthesized imageCP1 looking down the vehicle 2 and the surrounding areas of the vehicle2 by using the surrounding images AP(F), AP(L), AP(R) and the vehiclebody image 10. The synthesized image CP1 is an image looking down thefront of the vehicle 2 from an oblique left-rear and upper direction andrepresents the left area of the vehicle 2.

<1-4. Setting of Virtual Perspective>

In the below, a method by which the image generation unit 81 b sets thevirtual perspective VP is described in detail. FIGS. 7 to 12 depict amethod by which the image generation unit 81 b sets the virtualperspective VP. In the respective drawings, a direction and anorientation are appropriately indicated using a three-dimensional XYZCartesian coordinate system cc. The respective coordinate axes of theCartesian coordinate system cc are relatively fixed with respect to thevehicle 2. That is, a left-right direction of the vehicle 2 is theX-axis direction, a longitudinal direction of the vehicle 2 is theY-axis direction, and the vertical direction is the Z-axis direction.Also, the right side of the vehicle 2 is +X side, the front side of thevehicle 2 is +Y side, and the vertically upper side is +Z side.Therefore, the left side of the vehicle 2 is −X side, the rear side ofthe vehicle 2 is −Y side, and the vertically lower side is −Z side.

FIG. 7 depicts the vehicle 2, as viewed from the vertically upperdirection (+Z side), and also illustrates five reference virtualperspectives VPa (VPat, VPaf, VPab, VPal, VPar) of the virtualperspectives VP.

The five reference virtual perspectives VPa include five referencepositions (VLt, VLf, VLb, VLl, VLr), five movement center points RC(RCt, RCf, RCb, RCl, RCr) and five reference directions (VDt, VDf, VDb,VDtl, VDr), respectively.

The reference position VLt is located immediately above the vehicle 2.The reference position VLf is located immediately above the vehicle 2and at a more forward position (+Y side). The reference position VLb islocated immediately above the vehicle 2 and at a more rearward position(−Y side). The reference position VLl is located at an oblique left-rearposition of the vehicle 2 (−Y side and −X side). The reference positionVLr is located at an oblique right-rear position of the vehicle 2 (+Xside and −Y side). Heights (+Z side) of the respective referencepositions VL are the same from a ground contact surface GR on which thevehicle 2 is contacted. For example, the height is twice as high as thevehicle.

FIG. 8 depicts the vehicle 2, as viewed from the right side (+X side) inthe horizontal direction, and illustrates the movement center point RCand the reference direction VD. The movement center point RC is areference point becoming a center when the virtual perspective VP moves.Therefore, even when the perspective position of the virtual perspectiveVP moves, the line of sight faces towards the movement center point RCall the time. According to this configuration, it is possible to providea synthesized image enabling the user to feel as if the user were movingwhile seeing the imaging subject. A method of moving the position of thevirtual perspective VP by using the movement center point RC will bedescribed later.

The movement center point RCt is a specific point set at a specificposition of the vehicle 2. The movement center point RCt is positionedat a center of the vehicle 2. The movement center point RCf ispositioned at a center of the vehicle 2 in the left-right direction andat a more forward position (+Y side) than the front end of the vehicle2. The movement center point RCb is positioned at the center of thevehicle 2 in the left-right direction and at a more rearward position(−Y side) than the rear end of the vehicle 2. The movement center pointRCl is positioned at a center of the vehicle 2 in the longitudinaldirection and at an outermore position (−X side) that the left side ofthe vehicle 2. The movement center point RCr is positioned at the centerof the vehicle 2 in the longitudinal direction and at an outermoreposition (+X side) that the right side of the vehicle 2. A height (+Zside) of each movement center point RC is a height h of an eye line ofthe user sitting in the vehicle 2.

The reference direction VDt faces a direction (−Z side) from thereference position VLt towards the movement center point RCt. Thereference direction VDf faces a direction (−Z side and +Y side) from thereference position VLf towards the movement center point RCf. Thereference direction VDb faces a direction (−Z side and −Y side) from thereference position VLb towards the movement center point RCb. Thereference direction VDl faces a direction (−Z side and +Y side) from thereference position VLl towards the movement center point RCl. Thereference direction VDr faces a direction (−Z side and +Y side) from thereference position VLr towards the movement center point RCr.

Like this, the virtual perspective VP is a perspective viewing themovement center point RC from the perspective position VL. Also, areference virtual perspective VPat is a perspective looking down thevehicle 2 immediately above the vehicle (top view). A reference virtualperspective VPaf is a perspective viewing the front of the vehicle 2from a front-upper direction (front view). A reference virtualperspective VPab is a perspective viewing the rear of the vehicle 2 froma rear-upper direction (back view). A reference virtual perspective VPalis a perspective viewing the left area of the vehicle 2 from an obliqueleft-rear and upper direction (left side view). A reference virtualperspective VPar is a perspective viewing the right area of the vehicle2 from an oblique right-rear and upper direction (right side view).

The reference virtual perspective VPa is selected by the user. Theuser's selection is made by a touch operation on a touch panel buttonassociated with each reference virtual perspective VPa. That is, whenthe user selects any one reference virtual perspective VPa while thesynthesized image CP is displayed on the display, the image generationunit 81 b generates a synthesized image viewed from the selectedreference virtual perspective VPa. Thereby, even when the virtualperspective cannot be returned to the reference virtual perspective VPaafter diversely changing the position of the virtual perspective, theuser can easily set the virtual perspective to the reference virtualperspective VPa by the touch operation on the touch panel button.

At an initial stage of the image display before the user selects aperspective, any one of the reference virtual perspectives VPa is set inadvance. At this time, it is preferably to generate the synthesizedimage CP at the reference virtual perspective VPat looking down thevehicle 2 immediately above the vehicle. The reason is that thesynthesized image CP can present the user with the wide areas around thevehicle 2 and is thus suitable for the initial display.

In the below, a method of moving the perspective position VL by usingthe movement center point RC is described. First, a method of moving theperspective position VL in the left-right direction (horizontaldirection) while the user sees the display is described with referenceto FIGS. 9 and 10. The movement of the perspective position VL, whichwill be described below, is performed in correspondence to the user'sflick operation on the touch panel in the left-right direction (thehorizontal direction).

FIG. 9 depicts the vehicle 2 viewed from the vertically upper direction(+Z side), and also illustrates a movement path of the referenceposition VLl of the reference virtual perspective VPal. The referenceposition VLl moves along a movement path OBlh having the movement centerpoint RCl as a center. The movement of the perspective position VL isbased on the Cartesian coordinate system cc (the world coordinatesystem) that is relatively fixed to the vehicle 2 having a position ofthe movement center point RCl as an origin. The coordinate axis becominga movement reference of the reference position VLl is the Z axis of theCartesian coordinate system cc at the position of the movement centerpoint RC.

FIG. 10 depicts the vehicle 2 viewed from the right side (+X side) inthe horizontal direction, and also illustrates the movement path of thereference position VLl of the reference virtual perspective VPal, likeFIG. 9. The reference position VLl moves along the movement path OBlhhaving the movement center point RCl as a center. The coordinate axisbecoming a movement reference of the reference position VLl is the Zaxis (AXl) of the Cartesian coordinate system cc at the position of themovement center point RC.

In FIGS. 9 and 10, the reference direction VDl always faces thedirection from the reference position VLl towards the movement centerpoint RCl even when the reference position VLl is located at anyposition on the movement path OBlh. Therefore, when the referenceposition VLl moves along the movement path OBlh, the user seeing thedisplay 83 feels as if the image moves laterally.

When the user performs the flick operation from the left directiontowards the right direction (in the horizontal direction) on the touchpanel 83 a, the reference position VLl moves in a counterclockwisedirection along the movement path OBlh. On the other hand, when the userperforms the flick operation from the right direction towards the leftdirection (in the horizontal direction) on the touch panel 83 a, thereference position VLl moves in a clockwise direction along the movementpath OBlh. Thereby, the direction of the user's flick operation and themoving direction of the image coincide with each other, and the user canintuitively perform the touch panel operation.

In the below, a method of moving the perspective position VL in theupper-lower direction (vertical direction) while the user sees thedisplay is described with reference to FIGS. 11 and 12. The movement ofthe perspective position VL, which will be described below, is performedin correspondence to the user's flick operation on the touch panel inthe upper-lower direction (vertical direction).

In FIGS. 11 and 12, the direction and the orientation are appropriatelyshown using the three-dimensional XYZ Cartesian coordinate system VPcc(the perspective coordinate system), in addition to thethree-dimensional XYZ Cartesian coordinate system cc. The respectivecoordinate axes of the Cartesian coordinate system VPcc are relativelyfixed with respect to the virtual perspective VP. That is, theleft-right direction of the virtual perspective VP is the X-axis (VPx)direction, the longitudinal direction of the virtual perspective VP isthe Y-axis (VPy) direction, and the vertical direction of the virtualperspective VP is the Z-axis (VPz) direction. Also, the right side ofthe virtual perspective VP is +X side, the front side of the virtualperspective VP is +Y side, and the vertically upper side of the virtualperspective VP is +Z side. Therefore, the left side of the virtualperspective VP is −X side, the rear side of the virtual perspective VPis −Y side, and the vertically lower side is −Z side.

FIG. 11 depicts the vehicle 2 viewed from the vertically upper direction(+Z side), and also illustrates a movement path of the referenceposition VLl of the reference virtual perspective VPal. The referenceposition VLl moves along a movement path OBlv having the movement centerpoint RCl as a center. The movement of the perspective position VL isbased on the Cartesian coordinate system VPcc that is relatively fixedto the virtual perspective VP having a position of the movement centerpoint RCl as an origin. The coordinate axis becoming a movementreference of the reference position VLl is the X axis (AXlv) of theCartesian coordinate system VPcc at the position of the movement centerpoint RCl.

FIG. 12 depicts the vehicle 2 viewed from the left side (−X side) in thehorizontal direction, and also illustrates the movement path of thereference position VLl of the reference virtual perspective VPal, likeFIG. 11. The reference position VLl moves along the movement path OBlhhaving the movement center point RCl as a center. The coordinate axisbecoming a movement reference of the reference position VLl is the Xaxis of the Cartesian coordinate system cc at the position of themovement center point RC.

In FIGS. 11 and 12, the reference direction VDl always faces thedirection from the reference position VLl towards the movement centerpoint RCl even when the reference position VLl is located at anyposition on the movement path OBlv. Therefore, when the referenceposition VLl moves along the movement path OBlv, the user seeing thedisplay 83 feels as if the image moves in the upper-lower direction.

In the meantime, the movement path OBlv is set above the ground contactsurface GR of the vehicle 2. Therefore, the reference position VLl movesalong the movement path OBlv shown with the broken line and does notmove along a movement path OBlx shown with the solid line. Thereby, itis possible to prevent an image display in which the vehicle 2 is viewedfrom below the ground contact surface, which cannot be usually assumed.Therefore, the user can move the perspective position without anyuncomfortable feeling.

When the user performs the flick operation from the upper directiontowards the lower direction (in the vertical direction) on the touchpanel 83 a, the reference position VLl moves in the clockwise directionalong the movement path OBlv. On the other hand, when the user performsthe flick operation from the lower direction towards the upper direction(in the vertical direction) on the touch panel 83 a, the referenceposition VLl moved in the counterclockwise direction along the movementpath OBlv. Thereby, the direction of the user's flick operation and themoving direction of the image coincide with each other, and the user canintuitively perform the touch panel operation.

<1-5. Display Examples of Synthesized Image>

In the below, examples of the synthesized image CP that is to bedisplayed on the display 83 are described with reference to FIGS. 13 to24.

FIG. 13 depicts an example where a synthesized image CPt1 is displayedon the display 83. The synthesized image CPt1 is an image where thevehicle 2 is viewed from the reference virtual perspective VPat set asthe virtual perspective VP. The synthesized image CPt1 displays thevehicle body image 10, in addition to the surrounding image indicativeof the surroundings of the vehicle 2. The synthesized image CPt1 isdisplayed at the initial display stage of the synthesized image CP andwhen the user touches a touch panel button TB13 indicative of thesurroundings of the vehicle 2. The user can collectively check thesurrounding situations of the vehicle 2 by referring to the synthesizedimage CPt1.

FIG. 14 depicts an example where a synthesized image CPt2 is displayedon the display 83. The synthesized image CPt2 is an image where thevehicle 2 is viewed from the reference virtual perspective VPat set bymoving the reference position in the clockwise direction along themovement path OBlh of FIG. 9 after the display of the synthesized imageCPt1 (FIG. 13). The synthesized image CPt2 displays the vehicle bodyimage 10, in addition to the surrounding image indicative of thesurroundings of the vehicle 2 displayed by rotating leftwards thevehicle while the user sees the display 8. The synthesized image CPt2 isdisplayed when a flick operation FH is performed from the left directiontowards the right direction (in the horizontal direction) on the touchpanel 83 a with the synthesized image CPt1 (FIG. 13) being displayed.The user can check the surrounding situations of the vehicle 2 at adifferent angle from the synthesized image CPt1 by referring to thesynthesized image CPt2.

FIG. 15 depicts an example where a synthesized image CPt3 is displayedon the display 83. The synthesized image CPt3 is an image where thevehicle 2 is viewed from the reference virtual perspective VPat set bymoving the reference position in the counterclockwise direction alongthe movement path OBlh of FIG. 12 after the display of the synthesizedimage CPt1 (FIG. 13). The synthesized image CPt3 is displayed to includea part immediately below the front end of the vehicle 2. The synthesizedimage CPt3 is displayed when a flick operation FV is performed from theupper direction towards the lower direction (in the vertical direction)on the touch panel 83 a with the synthesized image CPt1 (FIG. 13) beingdisplayed. The user can check the surrounding situations of the vehicle2 including the part immediately below the front end of the vehicle 2 byreferring to the synthesized image CPt3.

FIG. 16 depicts an example where a synthesized image CPf1 is displayedon the display 83. The synthesized image CPf1 is an image where thevehicle 2 is viewed from the reference virtual perspective VPaf set asthe virtual perspective VP. The synthesized image CPf1 displays thevehicle body image 10, in addition to the surrounding image indicativeof the front of the vehicle 2. The synthesized image CPt1 is displayedwhen the user touches a touch panel button TB16 indicative of the frontof the vehicle 2. The user can check the front situations of the vehicle2 by referring to the synthesized image CPf1.

FIG. 17 depicts an example where a synthesized image CPf2 is displayedon the display 83. The synthesized image CPf2 is an image where thevehicle 2 is viewed from the reference virtual perspective VPaf set bymoving the reference position in the clockwise direction along themovement path OBlh of FIG. 9 after the display of the synthesized imageCPf1 (FIG. 16). The synthesized image CPf2 displays the vehicle bodyimage 10, in addition to the surrounding image indicative of thesurroundings of the vehicle 2 displayed by rotating leftwards thevehicle while the user sees the display 8. The synthesized image CPf2 isdisplayed when the flick operation FH is performed from the leftdirection towards the right direction (in the horizontal direction) onthe touch panel 83 a with the synthesized image CPf1 (FIG. 16) beingdisplayed. The user can check the front situations of the vehicle 2 at adifferent angle from the synthesized image CPf1 by referring to thesynthesized image CPf2.

FIG. 18 depicts an example where a synthesized image CPf3 is displayedon the display 83. The synthesized image CPf3 is an image where thevehicle 2 is viewed from the reference virtual perspective VPaf set bymoving the reference position in the counterclockwise direction alongthe movement path OBlh of FIG. 12 after the display of the synthesizedimage CPf1 (FIG. 13). The synthesized image CPf3 displays the front areaof the vehicle 2 in more detail than the synthesized image CPf1. Thesynthesized image CPf3 is displayed when the flick operation FV isperformed from the upper direction towards the lower direction (in thevertical direction) on the touch panel 83 a with the synthesized imageCPf1 (FIG. 16) being displayed. The user can check the front situationsof the vehicle 2 in detail by referring to the synthesized image CPf3.

FIG. 19 depicts an example where a synthesized image CPb1 is displayedon the display 83. The synthesized image CPb1 is an image where thevehicle 2 is viewed from the reference virtual perspective VPab set asthe virtual perspective VP. The synthesized image CPb1 displays thevehicle body image 10, in addition to the surrounding image indicativeof the rear of the vehicle 2. The synthesized image CPb1 is displayedwhen the user touches a touch panel button TB19 indicative of the rearof the vehicle 2. The user can check the rear situations of the vehicle2 by referring to the synthesized image CPb1.

FIG. 20 depicts an example where a synthesized image CPb2 is displayedon the display 83. The synthesized image CPb2 is an image where thevehicle 2 is viewed from the reference virtual perspective VPab set bymoving the reference position in the clockwise direction along themovement path OBlh of FIG. 9 after the display of the synthesized imageCPb1 (FIG. 19). The synthesized image CPb2 displays the vehicle bodyimage 10, in addition to the surrounding image indicative of the rear ofthe vehicle 2 displayed by moving leftwards the vehicle while the usersees the display 8. The synthesized image CPb2 is displayed when theflick operation FH is performed from the left direction towards theright direction (in the horizontal direction) on the touch panel 83 awith the synthesized image CPb1 (FIG. 19) being displayed. The user cancheck the rear situations of the vehicle 2 at a different angle from thesynthesized image CPb1 by referring to the synthesized image CPb2.

FIG. 21 depicts an example where a synthesized image CPb3 is displayedon the display 83. The synthesized image CPb3 is an image where thevehicle 2 is viewed from the reference virtual perspective VPab set bymoving the reference position in the counterclockwise direction alongthe movement path OBlh of FIG. 12 after the display of the synthesizedimage CPb1 (FIG. 19). The synthesized image CPb3 displays the rear areaof the vehicle 2 in more detail than the synthesized image CPb1. Thesynthesized image CPb3 is displayed when the flick operation FV isperformed from the upper direction towards the lower direction (in thevertical direction) on the touch panel 83 a with the synthesized imageCPb1 (FIG. 16) being displayed. The user can check the rear situationsof the vehicle 2 in detail by referring to the synthesized image CPb3.

FIG. 22 depicts an example where a synthesized image CPl1 is displayedon the display 83. The synthesized image CPl1 is an image where thevehicle 2 is viewed from the reference virtual perspective VPal set asthe virtual perspective VP. The synthesized image CPl1 displays thevehicle body image 10, in addition to the surrounding image indicativeof the left of the vehicle 2. The synthesized image CPl1 is displayedwhen the user touches a touch panel button TB22 indicative of the leftof the vehicle 2. The user can check the left situations of the vehicle2 by referring to the synthesized image CPl1.

FIG. 23 depicts an example where a synthesized image CPl2 is displayedon the display 83. The synthesized image CPl2 is an image where thevehicle 2 is viewed from the reference virtual perspective VPal set bymoving the reference position in the clockwise direction along themovement path OBlh of FIG. 9 after the display of the synthesized imageCPl1 (FIG. 22). The synthesized image CPl2 displays the vehicle bodyimage 10, in addition to the surrounding image indicative of the left ofthe vehicle 2 displayed by moving leftwards the vehicle while the usersees the display 8. The synthesized image CPl2 is displayed when theflick operation FH is performed from the left direction towards theright direction (in the horizontal direction) on the touch panel 83 awith the synthesized image CPl1 (FIG. 22) being displayed. The user cancheck the left situations of the vehicle 2 at a different angle from thesynthesized image CPl1 by referring to the synthesized image CPl2.

FIG. 24 depicts an example where a synthesized image CPl3 is displayedon the display 83. The synthesized image CPl3 is an image where thevehicle 2 is viewed from the reference virtual perspective VPal set bymoving the reference position in the counterclockwise direction alongthe movement path OBlh of FIG. 12 after the display of the synthesizedimage CPl1 (FIG. 22). The synthesized image CPl3 displays the left areaof the vehicle 2 in more detail than the synthesized image CPl1. Thesynthesized image CPl3 is displayed when the flick operation FV isperformed from the upper direction towards the lower direction (in thevertical direction) on the touch panel 83 a with the synthesized imageCPl1 (FIG. 22) being displayed. The user can check the left situationsof the vehicle 2 in detail by referring to the synthesized image CPl3.

Regarding the synthesized image CP indicative of the right of thevehicle 2, the operation and control may be performed in a bilaterallysymmetric manner with the case described with reference to FIGS. 22 to24 depicting the left of the vehicle 2. The user can check the rightsituations of the vehicle 2 by referring to the synthesized image CPindicative of the right of the vehicle 2.

<1-6. Processing>

In the below, a processing sequence that is to be executed in the imagedisplay system 1 is described with reference to FIGS. 25 and 26. FIG. 25depicts a processing sequence that is to be executed by the imageacquisition device 3, the security device 5 and the portable terminal 8.FIG. 26 depicts a processing sequence that is to be executed by thealarm unit 6 and the portable terminal 8. This processing is repeatedlyexecuted with a predetermined period.

First, the security device 5 determines whether the monitoring sensor 5a has operated (step S101 in FIG. 25).

When it is determined that the monitoring sensor 5 a has operated (Yesin step S101), the security device 5 controls the mail notification unit5 b to transmit an electronic mail, which indicates that the monitoringsensor 5 a has operated, i.e., the previous phenomenon leading to thetheft has occurred in the vehicle 2, to the portable terminal 8 of theuser (step S102). As an example where the monitoring sensor 5 a hasoperated, a case where the monitoring sensor 5 a detects occurrence ofvibrations or inclination in the vehicle 2, breaking of the glass, aninvader into the vehicle 2 or the like may be cited.

When the security device 5 determines that the monitoring sensor 5 a hasnot operated (No in step S101) or when the mail notification unit 5 btransmits the electronic mail, the processing by the security device 5is over. The security device 5 resumes the processing afterpredetermined time.

When the communication unit 82 of the portable terminal 8 receives theelectronic mail transmitted from the mail notification unit 5 b, thedisplay control unit 81 c displays the contents of the electronic mailon the display 83 (step S201). The user checks the contents of theelectronic mail displayed on the display, and determines whether or notto display the surrounding image of the vehicle 2. When the user wantsthe display of the surrounding image of the vehicle 2, the user maytouch a predetermined position on the touch panel 83 a.

The operation detection unit 81 d determines whether the user hastouched the predetermined position on the touch panel 83 a, at which thesurrounding image is to be displayed (step S202).

When the operation detection unit 81 d determines that the user wantsthe display of the image because the user has touched the predeterminedposition on the touch panel 83 a, at which the surrounding image is tobe displayed (Yes in step S202), the notification unit 81 e transmits tothe image acquisition device 3 a signal for requesting transmission ofthe image (step S203).

When the operation detection unit 81 d determines that the user hastouched a predetermined position on the touch panel 83 a, whichindicates that the surrounding image is not to be displayed, i.e., theuser does not want the display of the image (No in step S202), theprocessing is over. The reason is that it is not necessary to continuethe processing since the user does not want the display of the image.

When the request reception unit 31 a of the image acquisition device 3receives from the portable terminal 8 the signal for requestingtransmission of the image, the camera control unit 31 b controls thecameras 4 (4F, 4B, 4L, 4R) to start the capturing (step S301).

When the image acquisition unit 31 c receives the image datacorresponding to the images captured by the cameras 4 (4F, 4B, 4L, 4R),the image transmission unit 31 d transmits the image data to theportable terminal 8 through the communication unit 32 (step S302).

When the image acquisition unit 81 a of the portable terminal 8 receivesthe image data transmitted from the image acquisition device 3, theimage generation unit 81 b sets the position and direction of thevirtual perspective for generating the surrounding image (step S204).When generating the surrounding image for the first time, the imagegeneration unit 81 b sets the position of the virtual perspectiveimmediately above the vehicle 2 and sets the direction of the virtualfield of view in the downward direction (top view). The virtualperspective is a perspective at which the user looks down the vehicle 2from a position immediately above the vehicle 2. The correspondingperspective is preferable as the position and direction of the virtualperspective that is first to be presented to the user. That is, sincethe entire surroundings of the vehicle are displayed, it is possible toextensively present the user with the situations.

After setting the virtual perspective, the image generation unit 81 bgenerates the surrounding image by the above-described methods. Then,the image generation unit 81 b reads out the vehicle body image data 84a from the storage unit 84, and generates a synthesized image bysynthesizing the vehicle body image into the generated surrounding image(step S205).

When the image generation unit 81 b generates the synthesized image, thedisplay control unit 81 c displays the synthesized image on the display83 (step S206). Thereby, the user can check the surrounding situationsof the vehicle 2.

When the display control unit 81 c displays the synthesized image on thedisplay 83, the operation detection unit 81 d determines whether theuser has performed the flick operation on the display 83 (step S207).

When the operation detection unit 81 d determines that the user hasperformed the flick operation (Yes in step S207), the image generationunit 81 b again sets the virtual perspective (step S204).

When the user has performed the flick operation in the left-rightdirection (horizontal direction) on the display 83, the image generationunit 81 b rotates the virtual perspective on the basis of the verticaldirection axis of the world coordinate system to set the position of thevirtual perspective, as described above.

When the flick operation is performed from the right towards the left onthe display 83, the image generation unit 81 b rotates the position ofthe virtual perspective in the counterclockwise direction, when seeingthe vertical direction axis of the world coordinate system from above.Also, when the flick operation is performed from the left towards theright on the display 83, the image generation unit 81 b rotates theposition of the virtual perspective in the clockwise direction, whenseeing the vertical direction axis of the world coordinate system fromabove.

When the user has performed the flick operation in the upper-lowerdirection (vertical direction) on the display 83, the image generationunit 81 b rotates the virtual perspective on the basis of the horizontaldirection axis of the perspective coordinate system to set the positionof the virtual perspective, as described above.

When the flick operation is performed from the upper towards the loweron the display 83, the image generation unit 81 b rotates the positionof the virtual perspective in the counterclockwise direction, whenseeing the horizontal direction axis of the perspective coordinatesystem from the right of the perspective. Also, when the flick operationis performed from the lower towards the upper on the display 83, theimage generation unit 81 b rotates the position of the virtualperspective in the clockwise direction, when seeing the horizontaldirection axis of the perspective coordinate system from the right ofthe perspective.

By rotating the position of the virtual perspective in this way, thedirection in which the user wants to move the perspective by the flickoperation and the moving direction of the image to be displayed coincidewith each other and the user can intuitively move the image through theoperation on the touch panel 83 a.

When the operation detection unit 81 d determines that the user has notperformed the flick operation (No in step S207), the operation detectionunit 81 d determines whether an operation of changing the virtualperspective to the reference perspective has been performed (step S208).The operation detection unit 81 d determines whether the user hastouched any one touch panel button indicative of the referenceperspective.

When the operation detection unit 81 d determines that an operation ofchanging the virtual perspective to the reference perspective has beenperformed (Yes in step S208), the image generation unit 81 b sets theposition and direction of the virtual perspective to the referenceperspective designated by the user's touch operation (step S204). Forexample, when the user desires a reference perspective for displayingthe left area of the vehicle 2, the image generation unit 81 b sets theposition and direction of the virtual perspective as shown in FIGS. 9and 10. In the meantime, the reference perspective includes fiveperspectives of the immediately above of the vehicle, the left of thevehicle 2, the right of the vehicle 2, the front of the vehicle 2 andthe rear of the vehicle 2. The position of the movement center point RC,which is a specific point set at the specific position of the vehicle,is set to a position corresponding to the user's desired referenceperspective.

On the other hand, when the operation detection unit 81 d determinesthat an operation of changing the virtual perspective to the referenceperspective has not been performed (No in step S208), the operationdetection unit 81 d determines whether the user intends to operate thealarm unit 6 mounted to the vehicle 2 (step S209). The operationdetection unit 81 d determines whether the user has touched apredetermined position on the touch panel 83 a, which indicates anoperation of the alarm unit.

When the operation detection unit 81 d determines that the user intendsto operate the alarm unit 6 (Yes in step S209), the notification unit 81e transmits a signal for requesting an operation of the alarm unit 6 tothe image acquisition device 3 (step S210).

When the notification unit 81 e transmits a signal for requesting anoperation of the alarm unit 6, the antitheft unit 31 e of the imageacquisition device 3 enables the alarm unit 6 to issue a warning (stepS401). In the meantime, the warning by the alarm unit 6 is over afterpredetermined time elapses. The predetermined time may be a time periodenough to warn a suspicious person. For example, the predetermined timeis 5 seconds. The user may also end the warning.

When the operation detection unit 81 d determines that the user does notintend to operate the alarm unit 6 (No in step S209), or when theantitheft unit 31 e enables the alarm unit 6 to issue the warning (stepS210), the operation detection unit 81 d determines whether the userintends to end the image display (step S211).

When the operation detection unit 81 d determines that the user intendsto end the image display (Yes in step S211), the notification unit 81 etransmits a signal for requesting capturing ending to the imageacquisition device 3 (step S212). When the notification unit 81 etransmits a signal for requesting the capturing ending to the imageacquisition device 3, the processing by the portable terminal 8 is over.

When the operation detection unit 81 d determines that the user does notintend to end the image display (No in step S211), the display controlunit 81 c continues to generate and display the image, and the portableterminal 8 again executes the processing of step S205 and thereafter.

When the image transmission unit 31 d transmits the image data in stepS302, the request reception unit 31 a determines whether the endingrequest signal for requesting the capturing ending has been transmittedfrom the portable terminal 8 (step S303). The image acquisition device 3repeatedly transmits the image data most recently obtained by thecameras 4 (4F, 4B, 4L, 4R) to the portable terminal 8 until the endingrequest signal is received. Thereby, the image generation unit 81 b ofthe portable terminal 8 can generate the surrounding image indicative ofthe surrounding situations of the vehicle 2 in substantially real timeon the basis of the most recently obtained image data.

When the request reception unit 31 a determines that the ending requestsignal for requesting the capturing ending has been transmitted from theportable terminal 8 (Yes in step S303), the camera control unit 31 bcontrols the cameras 4 (4F, 4B, 4L, 4R) to stop the capturing (stepS304). When the camera control unit 31 b controls the cameras 4 (4F, 4B,4L, 4R) to stop the capturing, the processing by the image acquisitiondevice 3 is over.

As described above, according to the image display system 1 of the firstillustrative embodiment, the position of the virtual perspective ischanged and the synthesized image is displayed, based on the user'soperation. Thereby, it is possible to easily display the imaging subjectfrom the user's desired perspective.

2. Second Illustrative Embodiment

<2-1. Outline>

In the below, a second illustrative embodiment is described. In thefirst illustrative embodiment, when the perspective position VL islocated immediately above the vehicle 2 and the line of sight VD facestowards the downward direction (−Z side) (i.e., the top view), themovement of the perspective position VL, in response to the user's flickoperation in the left-right direction (horizontal direction), is basedon the vertical axis (Z axis) of the Cartesian coordinate system cc.Thereby, the synthesized image CP is displayed with being rotatedleftward or rightward.

However, even when the synthesized image CP is displayed with beingrotated, the corresponding display does not present the user with a newsurrounding area.

In the second illustrative embodiment, the movement of the perspectiveposition VL in the top view is based on the Y axis of the Cartesiancoordinate system cc, which is the longitudinal axis of the vehicle 2.Thereby, in the top view, when the user performs the flick operation inthe left-right direction (horizontal direction) on the touch panel 83 a,the left and right areas of the vehicle 2 including the sides of thevehicle 2 are displayed. For this reason, the user can check the leftand right areas of the vehicle 2 in detail.

In the below, the differences from the first illustrative embodiment aremainly described, and the overlapping descriptions as to the same orsimilar configurations and operations as or to the first illustrativeembodiment are omitted.

<2-2. Configuration>

FIG. 27 depicts a configuration of the portable terminal 8 of the imagedisplay system 1 according to the second illustrative embodiment. Themain difference from the first illustrative embodiment is that thecontrol unit 81 of the portable terminal 8 has a coordinate axisconversion unit 81 f.

The coordinate axis conversion unit 81 f converts the coordinate axisbecoming a movement reference of the perspective position VL from thevertical axis (Z axis) of the Cartesian coordinate system cc to thelongitudinal axis (Y axis) of the vehicle when the virtual perspectiveis a top view.

<2-3. Setting of Virtual Perspective>

In the below, a method of moving the perspective position VL in theleft-right direction (horizontal direction) while the user sees thedisplay in the top view display is described with reference to FIGS. 28and 29. The movement of the perspective position VL to be describedbelow is performed in correspondence to the user's flick operation inthe left-right direction (horizontal direction) on the touch panel, inthe top view display.

FIG. 28 depicts the vehicle 2, as viewed from the vertically upperdirection (+Z side), and also illustrates a moving path of the referenceposition VLt of the reference virtual perspective VPat. The referenceposition VLt moves along the movement path OBth having the movementcenter point RCt as a center. The movement of the reference position VLtis based on the Cartesian coordinate system cc that is relatively fixedto the virtual perspective VP having the position of the movement centerpoint RCt as an origin. The coordinate axis becoming a movementreference of the reference position VLt is the Y axis (AXth) of theCartesian coordinate system cc at the position of the movement centerpoint RCt, i.e., the longitudinal axis of the vehicle 2.

FIG. 29 depicts the vehicle 2, as viewed from the rear (−Y side) in thehorizontal direction, and also illustrates the moving path of thereference position VLt of the reference virtual perspective VPat, likeFIG. 28. The reference position VLt moves along the movement path OBthhaving the movement center point RCt as a center. The movement path OBthis a circle, as seen from the rear (−Y side) in the horizontaldirection. The coordinate axis becoming a movement reference of thereference position VLt is the Y axis of the Cartesian coordinate systemcc at the position of the movement center point RCt.

In FIGS. 28 and 29, the reference direction VDt always faces a directionfrom the reference position VLt towards the movement center point RCt,even when the reference position VLt is located at any position on themovement path OBth. Therefore, when the reference position VLt movesalong the movement path OBth, the user seeing the display 83 feels as ifthe image moves in the left-right direction (horizontal direction). Inparticular, since the coordinate axis becoming the movement reference ofthe reference position VLt is set to the Y axis of the Cartesiancoordinate system cc at the position of the movement center point RCt,the user can refer to the surrounding image of the vehicle 2 as if theimage went round the lateral sides of the vehicle 2.

In the meantime, the movement path OBth is not set below the groundcontact surface GR of the vehicle 2. Therefore, the reference positionVLt moves along the movement path OBth shown with the broken line anddoes not move along a movement path OBtx shown with the solid line.

When the user performs the flick operation from the left directiontowards the right direction (in the horizontal direction) on the touchpanel 83 a, the reference position VLt moves in the counterclockwisedirection along the movement path OBth. On the other hand, when the userperforms the flick operation from the right direction towards the leftdirection (in the horizontal direction) on the touch panel 83 a, thereference position VLt moves in the clockwise direction along themovement path OBth. Thereby, since the direction of the user's flickoperation and the moving direction of the image coincide with eachother, the user can intuitively perform the touch panel operation.

<2-4. Display Examples of Synthesized Image>

An upper figure of FIG. 13 depicts an example where the synthesizedimage CPt1 is displayed on the display 83. The synthesized image CPt1 isan image where the vehicle 2 is viewed from the reference virtualperspective VPat set as the virtual perspective VP. That is, thesynthesized image CPt1 is a synthesized image when the virtualperspective is a top view.

A lower figure of FIG. 30 depicts an example where a synthesized imageCPt4 is displayed on the display 83. The synthesized image CPt4 is animage displayed when the coordinate axis for moving the perspectiveposition VL is converted from the vertical axis (Z axis) of theCartesian coordinate system cc to the longitudinal axis (Y axis) of thevehicle after the display of the synthesized image CPt1, i.e., an imagewhere the vehicle 2 is viewed from the reference virtual perspectiveVPat set by moving the reference position in the counterclockwisedirection along the movement path OBth of FIG. 29. The synthesized imageCPt4 displays the vehicle body image 10, in addition to the surroundingimage of the vehicle 2 including the lateral side of the vehicle 2. Forthis reason, the user can check in detail the left and right areas ofthe vehicle 2 from the top view. The synthesized image CPt4 is displayedwhen the flick operation FH is performed from the left direction towardsthe right direction (in the horizontal direction) on the touch panel 83a with the synthesized image CPt1 being displayed. The user can check indetail the left and right areas of the vehicle 2 including the lateralsides of the vehicle 2 by referring to the synthesized image CPt4.

<2-5. Processing>

In the below, a processing sequence that is to be executed in the imagedisplay system 1 of the second illustrative embodiment is described withreference to FIGS. 31 and 32. FIG. 31 depicts a processing sequence thatis to be executed by the image acquisition device 3, the security device5 and the portable terminal 8. This processing sequence is differentfrom the processing sequence of the first illustrative embodiment shownin FIG. 25, in that processing of step S209 is included.

First, the image generation unit 81 b sets the position of the virtualperspective and the direction of the virtual field of view forgenerating the surrounding image (step S204). When generating thesurrounding image for the first time, the image generation unit 81 bsets the position of the virtual perspective immediately above thevehicle 2 and sets the direction of the virtual field of view in thedownward direction (top view). Also, the coordinate axis conversion unit81 f sets the longitudinal axis (Y axis) of the vehicle as the axisbecoming the movement reference of the perspective position VL.

When the processing of step S205, step S206 and step S207 is executed,the operation detection unit 81 d determines whether an operation ofchanging the virtual perspective to the reference perspective has beenperformed (step S208). The operation detection unit 81 d determineswhether the user has touched any one touch panel button indicative ofthe reference perspective.

When the operation detection unit 81 d determines that an operation ofchanging the virtual perspective to the reference perspective has beenperformed (Yes in step S208), the image generation unit 81 b executescoordinate axis setting processing (step S209).

FIG. 32 depicts the coordinate axis setting processing in detail. Whenthe processing proceeds to the coordinate axis setting processing (stepS209), the operation detection unit 81 d determines whether the virtualperspective has been changed to the perspective of a top view (stepS401).

When the operation detection unit 81 d determines that the virtualperspective has been changed to the perspective of a top view (Yes instep S401), the coordinate axis conversion unit 81 f sets thelongitudinal axis (Y axis) of the vehicle as the coordinate axisbecoming the movement reference of the perspective position VL (stepS402).

When the operation detection unit 81 d determines that the virtualperspective has been changed to a perspective rather than theperspective of a top view (No in step S401), the coordinate axisconversion unit 81 f sets the vertical axis (Z axis) as the coordinateaxis becoming the movement reference of the perspective position VL(step S403).

When the processing of step S402 or step S403 is executed, theprocessing returns to FIG. 31 and the processing of step S204 andthereafter is again executed.

As described above, according to the image display system 1 of thesecond illustrative embodiment, in the top view, the movement of theperspective position VL is made on the basis of the axis (Y axis) of theCartesian coordinate system cc, which is the longitudinal axis of thevehicle 2. Thereby, in the top view, when the user performs the flickoperation in the left-right direction (horizontal direction) on thetouch panel 83 a, the left and right areas of the vehicle 2 includingthe sides of the vehicle 2 are displayed. For this reason, the user cancheck in detail the left and right areas of the vehicle 2.

3. Modified Embodiments

The present invention is not limited to the above illustrativeembodiments, and a variety of changes can be made. In the below, themodified embodiments are described. In the meantime, the aboveillustrative embodiments and the modified embodiments can beappropriately combined.

In the respective illustrative embodiments, the image acquisition device3 is configured to start the capturing upon the reception of the requestfor image transmission from the user. However, the image acquisitiondevice 3 may be configured to start the capturing before the request forimage transmission is received from the user, i.e., upon the operationof the monitoring sensor 5 a. In this case, the user can refer to thesurrounding situations of the vehicle 2 from when an abnormality, whichcauses the monitoring sensor 5 a to operate, occurs in the vehicle.

FIG. 33 depicts an outline of an image display system 1 a in which theimage acquisition device 3 is configured to start the capturing upon theoperation of the monitoring sensor 5 a. When the monitoring sensor 5 adetects an abnormality of the vehicle 2, the security device 5 transmitsto the image acquisition device 3 a signal for requesting the capturingstart. When the image acquisition device 3 receives the signal, theimage acquisition device 3 operates the cameras 4 to start thecapturing. That is, the image acquisition device 3 starts the capturingupon the occurrence of the abnormality in the vehicle 2 without waitingfor the request for image transmission from the user. When the imageacquisition device 3 starts the capturing, the image acquisition device3 transmits the image data to an external server SV. Thereby, the imagedata is preserved in the server SV from when the abnormality hasoccurred in the vehicle 2. Therefore, when the user receives a mail,which notifies that the abnormality has occurred in the vehicle 2, fromthe security device 5, the user requests the server SV to transmit theimage. When the server SV receives the request for image transmission,the server SV transmits the image data to the portable terminal 8carried by the user from when the abnormality has occurred in thevehicle 2. Thereby, the user can refer to the surrounding situations ofthe vehicle 2 from when the monitoring sensor 5 a has operated, i.e.,the abnormality has occurred in the vehicle 2. Also, when the server SVis configured as a dedicated server for transmitting and receiving theimage data, there is no concern that the image data will be interceptedby the other person. That is, it is possible to increase theconfidentiality of the image data. In the meantime, when the user wantsto check the current surrounding situations of the vehicle 2, the usercan request the server SV to transmit the current image data. In thiscase, the server SV transmits the current image data withouttransmitting the image data from the occurrence of the abnormality untilnow.

The other modified embodiments are described. In the respectiveillustrative embodiments, the image acquisition device 3, the cameras 4,the security device 5 and the alarm unit 6 are mounted on the vehicle 2.However, the corresponding devices may be mounted to lands, houses,buildings or products to be monitored.

In the respective illustrative embodiments, the user performs the inputoperation on the touch panel. However, the user may perform the inputoperation through a push button-type switch such as arrow key as long asthe user's input operation can be discriminated.

In the respective illustrative embodiments, the image acquisition device3 and the portable terminal 8 are separate devices. However, the imageacquisition device 3 and the portable terminal 8 may be configured as anintegrated device.

In the respective illustrative embodiments, the respective functions ofthe image display system 1 are implemented as the software based on theprogram. However, the respective functions of the image display system 1may be configured as electrical hardware circuits.

A Japanese Patent Application No. 2013-214014 filed on Oct. 11, 2013,which configures a part of the application, is herein incorporated.

The invention claimed is:
 1. An image display device comprising: atleast one processor programmed to: acquire a plurality of imagesobtained by capturing an imaging subject by using a plurality ofcameras, the imaging subject including a surrounding of a vehicle onwhich the plurality of cameras are disposed; synthesize the plurality ofimages and generate a synthesized image which shows the imaging subjectviewed from one of a plurality of reference virtual perspectives whichare at different positions with respect to the imaging subject; displaysimultaneously the synthesized image in a first area on a screen and aplurality of buttons in a second area on the screen, the first area andthe second area being provided side-by-side on the screen, the pluralityof buttons each corresponding to a respective one of the plurality ofreference virtual perspectives; detect a user operation performed in thesecond area on the screen, the user operation selecting one of theplurality of buttons; in response to detecting the user operation,change, in real-time, an entire area of the synthesized image to showthe imaging subject viewed from a selected one of the plurality ofreference virtual perspectives corresponding to the selected button;detect a touch operation performed in the first area on the screen, thetouch operation being different from the user operation and being atleast one of a flick operation, a pinch-in operation and a pinch-outoperation; and in response to detecting the touch operation, change, inreal-time, the entire area of the synthesized image to show the imagingsubject viewed from a virtual perspective that is moved along a single,continuous predetermined path over the vehicle in accordance with thetouch operation, wherein: the touch operation moves the virtualperspective from any point on the predetermined path in any directionalong the predetermined path, and the touch operation determines atiming at which the virtual perspective moves.
 2. The image displaydevice according to claim 1, wherein the synthesized image is an imageviewing a reference point set at a specific position of the imagingsubject from a position of the virtual perspective, the specificposition not changing with a changing position of the virtualperspective.
 3. The image display device according to claim 2, whereinthe processor is programmed to change the position of the virtualperspective based on (i) a world coordinate system in which thereference point is set as an origin with respect to the vehicle and (ii)a perspective coordinate system in which the reference point is set asan origin with respect to the virtual perspective.
 4. The image displaydevice according to claim 2, wherein a position of the reference pointis set by a user.
 5. The image display device according to claim 2,wherein the processor is programmed to change the position of thevirtual perspective about a vertical axis of a world coordinate systemwhen the touch operation is an operation indicative of a horizontaldirection on the screen.
 6. The image display device according to claim2, wherein the processor is programmed to change the position of thevirtual perspective about a horizontal axis of a perspective coordinatesystem when the touch operation is an operation indicative of a verticaldirection on the screen.
 7. The image display device according to claim6, wherein the processor is programmed to change the position of thevirtual perspective within a range above a ground contact surface of theimaging subject when the position of the virtual perspective is changedabout the horizontal axis of the perspective coordinate system.
 8. Theimage display device according to claim 2, wherein the processor isprogrammed to: when the touch operation indicative of a horizontaldirection on the screen is performed with the reference point beingviewed from the virtual perspective located immediately above thevehicle, change the position of the virtual perspective about alongitudinal axis of the vehicle.
 9. The image display device accordingto claim 1, wherein the plurality of buttons are five buttonscorresponding respectively to the reference virtual perspectives at anupper side, a front side, a rear side, a right side and a left side ofthe vehicle; and the processor is programmed to display, as an initialdisplay before detecting the user operation and the touch operation, thesynthesized image which shows the imaging subject viewed from thereference virtual perspective at the upper side of the vehicle.
 10. Theimage display device according to claim 1, wherein the plurality ofbuttons displayed in the second area on the screen comprise four buttonswhich correspond respectively to the reference virtual perspectives at afront side, a rear side, a right side and a left side of the vehicle,and are provided respectively at an upper side, a lower side, a rightside and a left side of the second area, the plurality of buttonsfurther comprise a button corresponding to one of the plurality ofreference virtual perspectives from which the synthesized image whichshows a wide area around the vehicle is generated, and the processor isprogrammed to display, as an initial display before detecting the useroperation and the touch operation, the synthesized image which shows thewide area around the vehicle.
 11. An image display system comprising: atleast one first processor included in an image acquisition device; andat least one second processor included in an image display devicecapable of performing communication with the image acquisition device,wherein: the first processor is programmed to: acquire a plurality ofimages obtained by capturing an imaging subject by using a plurality ofcameras, the imaging subject including a surrounding of a vehicle onwhich the plurality of cameras are disposed; receive from the imagedisplay device a request signal for requesting transmission of theplurality of images; and transmit the plurality of images based on therequest signal; and the second processor is programmed to: transmit tothe image acquisition device the request signal for requestingtransmission of the plurality of images; receive the plurality of imagesfrom the image acquisition device; synthesize the plurality of imagesand generate a synthesized image which shows the imaging subject viewedfrom one of a plurality of reference virtual perspectives which are atdifferent positions with respect to the imaging subject; displaysimultaneously the synthesized image in a first area on a screen and aplurality of buttons in a second area on the screen, the first area andthe second area being provided side-by-side on the screen, the pluralityof buttons each corresponding to a respective one of the plurality ofreference virtual perspectives; detect a user operation performed in thesecond area on the screen, the user operation selecting one of theplurality of buttons; in response to detecting the user operation,change, in real-time, an entire area of the synthesized image to showthe imaging subject viewed from a selected one of the plurality ofreference virtual perspectives corresponding to the selected button;detect a touch operation performed in the first area on the screen, thetouch operation being different from the user operation and being atleast one of a flick operation, a pinch-in operation and a pinch-outoperation; and in response to detecting the touch operation, change, inreal-time, the entire area of the synthesized image to show the imagingsubject viewed from a virtual perspective that is moved along a single,continuous predetermined path over the vehicle in accordance with thetouch operation, wherein: the touch operation moves the virtualperspective from any point on the predetermined path in any directionalong the predetermined path, and the touch operation determines atiming at which the virtual perspective moves.
 12. The image displaysystem according to claim 11, wherein: the image acquisition device ismounted on the vehicle; and the image display system comprises at leastone third processor that is programmed to: detect a previous phenomenonleading to theft of the vehicle; and notify the image display device ofthe detection of the previous phenomenon.
 13. An image display methodcomprising: acquiring a plurality of images obtained by capturing animaging subject by using a plurality of cameras, the imaging subjectincluding a surrounding of a vehicle on which the plurality of camerasare disposed; synthesizing the plurality of images and generating asynthesized image which shows the imaging subject viewed from one of aplurality of reference virtual perspectives which are at differentpositions with respect to the imaging subject; displaying simultaneouslythe synthesized image in a first area on a screen and a plurality ofbuttons in a second area on the screen, the first area and the secondarea being provided side-by-side on the screen, the plurality of buttonseach corresponding to a respective one of the plurality of referencevirtual perspectives; detecting a user operation performed in the secondarea on the screen, the user operation selecting one of the plurality ofbuttons; in response to detecting the user operation, changing, inreal-time, an entire area of the synthesized image to show the imagingsubject viewed from a selected one of the plurality of reference virtualperspectives corresponding to the selected button; detecting a touchoperation performed in the first area on the screen, the touch operationbeing different from the user operation and being at least one of aflick operation, a pinch-in operation and a pinch-out operation; and inresponse to detecting the touch operation, changing, in real-time, theentire area of the synthesized image to show the imaging subject viewedfrom a virtual perspective that is moved along a single, continuouspredetermined path over the vehicle in accordance with the touchoperation, wherein: the touch operation moves the virtual perspectivefrom any point on the predetermined path in any direction along thepredetermined path, and the touch operation determines a timing at whichthe virtual perspective moves.
 14. A non-transitory computer readablemedium storing a program configured to be executable by a computerincluded in an image display device configured to display an image, theprogram being configured to enable the computer to execute: acquiring aplurality of images obtained by capturing an imaging subject by using aplurality of cameras, the imaging subject including a surrounding of avehicle on which the plurality of cameras are disposed; synthesizing theplurality of images and generating a synthesized image which shows theimaging subject viewed from one of a plurality of reference virtualperspectives which are at different positions with respect to theimaging subject; displaying simultaneously the synthesized image in afirst area on a screen and a plurality of buttons in a second area onthe screen, the first area and the second area being providedside-by-side on the screen, the plurality of buttons each correspondingto a respective one of the plurality of reference virtual perspectives;detecting a user operation performed in the second area on the screen,the user operation selecting one of the plurality of buttons; inresponse to detecting the user operation, changing, in real-time, anentire area of the synthesized image to show the imaging subject viewedfrom a selected one of the plurality of reference virtual perspectivescorresponding to the selected button; detecting a touch operationperformed in the first area on the screen, the touch operation beingdifferent from the user operation and being at least one of a flickoperation, a pinch-in operation and a pinch-out operation; and inresponse to detecting the touch operation, changing, in real-time, theentire area of the synthesized image to show the imaging subject viewedfrom a virtual perspective that is moved along a single, continuouspredetermined path over the vehicle in accordance with the touchoperation, wherein: the touch operation moves the virtual perspectivefrom any point on the predetermined path in any direction along thepredetermined path, and the touch operation determines a timing at whichthe virtual perspective moves.